First off , no air filtration.Not a good thing, sure it looks cool and will probably give you some performance increase, but don't let anyone fool ya , internal combustion engines suck a lot of out side air and it has lots of things that just love to prematurely eat your rings and valve systems up and it will eventually get in the oil system too. But like every thing else its your call and some say it don't hurt nothin.

My flowmeister showed me how just putting a ring of modeling clay around the mouth of a carb changes its flow characteristics. It's effect is not so much a boost as it is a cure. Any sharp edge or corner causes the kind of turbulence that robs flow capacity.
The effect of an extended funnel into the carb only becomes significant at very high airflows.
You will note that many modern aircleaners already have a very short horn at the mouth of the carb, and the "Vortex Air Master" is a bolt-on for modern carbs.
But for real Panhead carbs, check out the "Raceway" cone at http://www.oldiron.net/" onclick="window.open(this.href);return false;!
(The aircleaner update is pretty nifty as well.)